New Issues With E-Filing Tax Returns

I am continuing to discover the ins and outs of e-filing income tax returns. One issue that has come to my attention is the EFIN number, a number that is assigned to corporate and partnership taxpayers by the Internal Revenue Service. This is required to e-file Federal and State income tax returns.

For Federal Tax Purposes, corporate taxpayers that are affiliated with one another usually file under one company and combine each company's taxable income and pay tax based on the combined amount. When I worked for BellSouth Corporation, the federal return that was filed was "BellSouth Corporation and Subsidiaries," which made up many different companies.

For many states, particularly southern states and many northeastern states, companies file returns as separate entities - this means that groups of, say, 10 companies that filed 1 federal return would file up to 10 separate returns in states like Georgia or North Carolina if each company had business operations there.

The question I am having to answer if what EFIN to use for companies that e-file 1 combined Federal return under a common EFIN but must e-file separate state returns. Should the same EFIN number be used for each company? This would seem to be the case, but I guess I will find out for sure soon.